Henry edward tfairbrother and edmund charrington



March 25, 1930. H. E. FAIRBROTHER ET AL 1,752,161

CARBRETOR FOR INTERNAL COMBUSTION ENGINES Filed Feb. 25 1926 Patented Mar. 25, 1930 UNITED STATES HENRY EDWARD FAIRBROTHER .AND EDMUND CHARRINGTON, OF LONDON, ENGLAND CARBURETOR FOR INTERNAL-COMBUSTION ENGINES Application led February 25, 1926, Serial No. 90,639, and in Great Britain May 11, 1925.

This invention relates to carburetors for internal combustion engines of the kind which comprises a controllable throttle valve and in which oil, petrol or other fuel is fed to a mixing chamber in the body of a carburetor through a duct or inlet under the control of a spring-pressed needlevalve, air being admitted to the mixing chamber, under the suctional action ofthe engine, through a hollow valvular member.

The invention consists in improvements the objectbeing, by suitably constructing and arranging the several parts of a carburetor relatively to one another, to permit the ratio of the air and fuel in the mixture fed through the throttle valve to an engine to be varied automatically and correctly in accordance with variations in the suctional action of the engine and the mixture to be fed thereto in quantity proper for any speed.

The invention will be described with reference to the accompanying drawing, wh1ch is a section of a carburetor embodying the invention. The body a of the carburetor is hollow or tubular and may conveniently be straight or, as shown in the drawing, L- shape, one end or limb being employed for the admission of air and the other end or limb for the accommodation of a suitablethrottle valve b for controlling the opening to the engine induction pipe which is not shown. Air is admitted to the carburetor through a number of lateral ports or openings c provided in the air admission end or limb, and it passes through a hollow valvular device or internal sleeve l which may be cylindrically or conically bored. The valve al is slidably mounted in the air admission end or limb of the body a and is, when the engine is at rest, closed at its outer end by the suitably shaped end of a screw-plug p adjustably screwed into the end of the said end or limb.

The plug p is provided at its inner end with a spigot or vno'se part p of a diameter smaller than the internal diameter of the air valve d. This nose part p is adapted to enter and obturate the open outer end of the air valve when the engine is at rest or being started.

When the engine is started and a suctional action occurs in the carburetor, the movable choke d is drawn away from the end of the adjusting screw-plug p, whereupon oil, petrol or other fuel is at once and alone drawn into the mixing chamber in the carburetor body a, as described below, but air will not be immediately drawn in through the above-mentioned lateral openings and movable valve because the spigot or nose p of the plug will at that time extend within and close the outer end of the air valve 0l. Air will not bedrawn in until the a-ir valve is in such position that the outer end of the air valve is drawn clear of that nose. There is thus at the starting of the engine, when a strong mixture is required, a period during which fuel alone is drawn intothe mixing chamber after which, when the outer end of the choke is drawn clear of the no'se p', air is drawn in simultaneously with the fuel. By varying the position of the nose p', the duration of the said period can be varied, for the purpose of varyin the strength o'f the fuel and air mixture w en the engine is started.

The air valve d at its outer end is completely open and is provided with an external flange e which, when the choke is drawn from its initial or normal position (which is that shown in the drawing) and further into the mixing chamber by the suctional action of the engine when at work, is adapted to engage against the shoulder f formed on the internal l wall of the carburetor body a as soon as the suctional action becomes suihciently great, the possible inward movement of the choke being thus limited in extent. The air valve at its inner end may be partially closed by means of an internally disposed annular flange g, a central aperture g being thereby formed.

The air admission openings c may be protected against the entry of dust and other matter bymeans of a sleeve piece a: formed of gauze or other suitable material andarranged to embrace a terminal portion of the air admission end or limb of the carburetor 95 body a.

Oil, petrol or other fuel is admitted through a circular passage or duct h provided for the purpose in the body a of the carburetor and formed with an annular valve seat m 100 eov with which a cone-shaped valve Z carried by a stem z cooperates to control the iow of fuel through a feed outlet Ic forming an extension of the duct beyond the outer end of the valve. The stem Z may be either cylindrical or tapered, and the valve Z is adapted to engage the seat m and to close the outlet opening therethrough when the engine is at rest. The coned valve Z is held against the seat m by means of a helical spring o. A stem piece j extends forwardly from the smaller end of the valve Z and through the feed outlet lc and is of such a length that it touches or nearly touches the inner end of the air valve d, so that the air valve, in its movement inwardly towards the mixing chamber, by its engagement withthe said stem piece j pushes the valve Z from the annular seat m whereupon fuel, and fuel alone, immediately and automatically flows past the seating and through the feed outlet k into the mixingchamber, for a predetermined periodbefore anyvair can pass through the air valve d on its Way to the mixing chamber.

The valve i is guided in its movements in the duct L by means of the enlarged portion 1' which is shaped or formed in a manner to allow fuel to pass from the fuel inlet or supply end t of the duct to its outlet orifice lc. The peripheral surface of the portion r may conveniently comprise cylindrical parts and flats s. AThe duct is, by means of a suitable -nose part union u, connected with a fuel supply .which is not indicated on the drawing., The air valve d in making an inward movement under the suctional action of the engine but beforje its outer flanged end e is clear of the p of the plug p, engages and pushes back 'the needle z' against the action of the helical spring o, the coned portion ,Z of the needle moving away from its seating and thus allowing the passage of fuel through 1the duct and outlet k into the mixing chamer y. I

The component parts of the carburetor are initially arranged or set to suit the engine when running slow, the amount of petrol, or

other fuel, allowed to escape being determined b varying the diameter of the needle partj re ative to the duct or orifice k through which it passes, and the amount of air admitted is determined by adjusting the posi'- tion of the screw-plug p relatively to the outer open end of the air valve.

When the engine speed is increased the proportionate amounts of fuel and air are maintained automatically in accordance with the increased suction produced, and in accordance with the respective aperture areas of the air and fuel passages.

Perfection may be obtained at higher speed by varying the size of the opening g at the back or inner end of the movable air valve, which-has the effect of altering the proportion of fuel and air passing into the chamber y formed in the body ofthe carbul retor.

The suction on the fuel jet can be varied to a considerable extent by means of the adjustable screw-plug p, and suction on the fuel l,

supply can be increased by turning the plug so as to close to a greater or less extent the air passage between it and the outer end of the air valve. The plug can be vlocked in anyadjusted position by means of the lock nut w.

Having thus described the nature of the said invention and the best means we know and the inner face of saidl wall, an open `ended tubular air valve slidably mounted within the casing between the said open end and the mixing chamber, ay lugging member adjustably mounted on lie open end of the casing and forming with said lateral Wall a passage for the flow of air from theinner ends of said ports in a vdirection away from the said open end of the casing and towards the air valve, said plugging member having a projecting nose part adapted to extend within and obturate the outer end of the air valve when the engine is at rest and for a predetermined period at the starting of the engine, a fuel supply duct having an outlet arranged to discharge fuel within the mixing chamber in a direction towards the said open end, a spring-pressed needle valve slidably mounted in and normally closing the fuel valve, said needle valve having means extendinginto the path of movement of and engaged by the air valve for opening the fuel valve when the air valve is moved by suction of the engine toward open position, the said needle valve opening means and air valve being so related that the fuel valve is partially opened before the air valve opens said air passage.

2. In an apparatus of the character described, the combination of a tubular casing having an open end, a mixture discharge end and a mixing chamber between said ends, said casing also having in its lateral wall adjacent its open end a series of radially disposed air admlssion ports of which the opposite ends are respectlvely on the outer face and the inner face of said wall, an open-ended tubular air valve slidably mounted within the casing between the said open'end and the mixing chamber, a fuelsupply duct having an outlet arranged to discharge fuel Within the mixing chamber in a direction towards the air valve, a spring-pressed needle valve slidably mounted in the duct, a cylindrical plug having a part adjustably ixed in the said open end of the casing and a part of reduced diameter extending within and longitudinally of the casing and forming with the lateral wall of the casing a. passage for the flow of air from the inner ends of said ports and through the air valve towards the mixing chamber, said plug having a second inwardly extending part of a further reduced diameter and of a predetermined length, which second part is, when the engine is at rest and at the starting thereof, surrounded by the outer end portion of the tubular air valve and closes said outer end portion, until the air valve sliding under the suctional action of the engine when at Work moves in a direction away from and clear of the said second part of the plug thereby opening the said passage for the supply ofvair to said chamber, and means controlled by the sliding movement of the air valve for shiftv ing the needle valve to admit fuel alone to the mixing chamber for a predetermined period at the starting of the engine. 3. In an apparatus of the character described, the combination of a tubular casing having an open end, a mixture discharge end and a mixing chamber between said ends, said casing also having in its lateral Wall` adjacent its open end a series of radially disposed air admission ports of which the opposite ends are respectively on the outer face and the inner face of said wall, an open-ended tubular air valve slidably mounted within the casing between the said open end and the mixing chamber, a plug member adjustably mounted on the open end of the casing and forming with said lateral wall a passage for the flow of air from the inner ends of said air admission ports in a direction away from the said open end of the casing and towards the air valve, said plug member having a projecting nose part adapted to extend within and obturate the outer end of the air valve when the engine is at rest and for a predetermined period at the starting of the engine, a fuel supply duct, connected to said casing and having a seat opening toward said mixing chamber, a valve in said duct movable toward and away from said seat, means normally urging said valve toward said seat, and a stem piece carried by said valve and actuated by the movement of the air valve while the air valve is obturatcd by said plug member during the starting of the engine to unseat said fuelvalve and admit fuel alone to the mixing chamber, said air valve in its further movement moving away from said plug member to open said air passage and further open said fuel valve. a

In testimony whereof we have signed our names to this specification.

HENRY EDVARD FAIRBROTHER.

EDMUND CHARRINGTON. 

